StringBuilder toString() method in Java with Examples

The toString() method of the StringBuilder class is the inbuilt method used to return a string representing the data contained by StringBuilder Object. A new String object is created and initialized to get the character sequence from this StringBuilder object and then String is returned by toString().

• It does not modify the original StringBuilder.
• The returned object is immutable because String is immutable.

public class Main {
    public static void main(String[] args) {

        // Creating StringBuilder object
        StringBuilder str = new StringBuilder("GeeksForGeeks");

        // Converting StringBuilder to String
        String result = str.toString();

        System.out.println("String: " + result);
    }
}

String: GeeksForGeeks

Explanation: The toString() method converts the contents of the StringBuilder into a String.

Syntax

public String toString()

Return Value: This method returns a String containing the characters currently stored in the StringBuilder.

Example: toString() After Modifying StringBuilder

public class Main {
    public static void main(String[] args) {

        StringBuilder builder = new StringBuilder("Hello");

        // Convert to String
        String str = builder.toString();

        // Modify StringBuilder
        builder.append(" World");

        System.out.println("StringBuilder: " + builder);
        System.out.println("String: " + str);
    }
}

StringBuilder: Hello World
String: Hello

Explanation: The String returned by toString() contains the contents of the StringBuilder at the time of conversion. Later changes to the StringBuilder do not affect the already-created String.

Example: Convert an Array of Strings into a Single String

public class Main {
    public static void main(String[] args) {

        String[] words = {"Are", "You", "A", "Programmer"};

        StringBuilder builder = new StringBuilder();

        for (String word : words) {
            if (builder.length() > 0) {
                builder.append(" ");
            }

            builder.append(word);
        }

        // Convert StringBuilder to String
        String result = builder.toString();

        System.out.println(
            "Single String: " + result
        );
    }
}

Single String: Are You A Programmer

Explanation: The array elements are appended to the StringBuilder with spaces between them. Finally, toString() converts the complete character sequence into a String.

Why Use toString() with StringBuilder?

• Converts to String: Converts the mutable StringBuilder content into an immutable String.
• Useful for returning results: Methods that require a String can use the result of toString().
• Works efficiently with StringBuilder: Multiple modifications can be performed before creating the final String.
• Preserves the current content: The returned String represents the contents at the time toString() is called.

Advantages of StringBuilder toString() Method

• Converts StringBuilder content into a String.
• Provides an immutable String result.
• Preserves the content at the time of conversion.
• Useful when a String is required as the final result.
• Simple and easy to use.
• Allows multiple modifications before converting to String.